diff --git a/OpenRA.Mods.Common/AI/SupportPowerDecision.cs b/OpenRA.Mods.Common/AI/SupportPowerDecision.cs
index b8f6d0ad6f..89c94d6a36 100644
--- a/OpenRA.Mods.Common/AI/SupportPowerDecision.cs
+++ b/OpenRA.Mods.Common/AI/SupportPowerDecision.cs
@@ -160,7 +160,12 @@ namespace OpenRA.Mods.Common.AI
 
 						case DecisionMetric.Health:
 							var health = a.TraitOrDefault<Health>();
-							return (health != null) ? (health.HP / health.MaxHP) * Attractiveness : 0;
+
+							if (health == null)
+								return 0;
+
+							// Cast to long to avoid overflow when multiplying by the health
+							return (int)((long)health.HP * Attractiveness / health.MaxHP);
 
 						default:
 							return Attractiveness;
diff --git a/OpenRA.Mods.Common/Activities/Sell.cs b/OpenRA.Mods.Common/Activities/Sell.cs
index c33eb812a5..49d2b1f84b 100644
--- a/OpenRA.Mods.Common/Activities/Sell.cs
+++ b/OpenRA.Mods.Common/Activities/Sell.cs
@@ -34,9 +34,12 @@ namespace OpenRA.Mods.Common.Activities
 
 		public override Activity Tick(Actor self)
 		{
-			var cost = self.GetSellValue();
+			var sellValue = self.GetSellValue();
 
-			var refund = (cost * sellableInfo.RefundPercent * (health == null ? 1 : health.HP)) / (100 * (health == null ? 1 : health.MaxHP));
+			// Cast to long to avoid overflow when multiplying by the health
+			var hp = health != null ? (long)health.HP : 1L;
+			var maxHP = health != null ? (long)health.MaxHP : 1L;
+			var refund = (int)((sellValue * sellableInfo.RefundPercent * hp) / (100 * maxHP));
 			playerResources.GiveCash(refund);
 
 			foreach (var ns in self.TraitsImplementing<INotifySold>())
diff --git a/OpenRA.Mods.Common/Activities/Transform.cs b/OpenRA.Mods.Common/Activities/Transform.cs
index 324bc1dfaa..5ff8c97767 100644
--- a/OpenRA.Mods.Common/Activities/Transform.cs
+++ b/OpenRA.Mods.Common/Activities/Transform.cs
@@ -122,7 +122,8 @@ namespace OpenRA.Mods.Common.Activities
 				var health = self.TraitOrDefault<Health>();
 				if (health != null)
 				{
-					var newHP = ForceHealthPercentage > 0 ? ForceHealthPercentage : (health.HP * 100) / health.MaxHP;
+					// Cast to long to avoid overflow when multiplying by the health
+					var newHP = ForceHealthPercentage > 0 ? ForceHealthPercentage : (int)(health.HP * 100L / health.MaxHP);
 					init.Add(new HealthInit(newHP));
 				}
 
diff --git a/OpenRA.Mods.Common/Traits/Captures.cs b/OpenRA.Mods.Common/Traits/Captures.cs
index 4a1def3d7f..155388c15e 100644
--- a/OpenRA.Mods.Common/Traits/Captures.cs
+++ b/OpenRA.Mods.Common/Traits/Captures.cs
@@ -109,7 +109,9 @@ namespace OpenRA.Mods.Common.Traits
 				}
 
 				var health = target.Trait<Health>();
-				var lowEnoughHealth = health.HP <= c.Info.CaptureThreshold * health.MaxHP / 100;
+
+				// Cast to long to avoid overflow when multiplying by the health
+				var lowEnoughHealth = health.HP <= (int)(c.Info.CaptureThreshold * (long)health.MaxHP / 100);
 
 				cursor = !capturesInfo.Sabotage || lowEnoughHealth || target.Owner.NonCombatant
 					? capturesInfo.EnterCursor : capturesInfo.SabotageCursor;
@@ -129,7 +131,9 @@ namespace OpenRA.Mods.Common.Traits
 				}
 
 				var health = target.Info.TraitInfoOrDefault<HealthInfo>();
-				var lowEnoughHealth = target.HP <= c.CaptureThreshold * health.HP / 100;
+
+				// Cast to long to avoid overflow when multiplying by the health
+				var lowEnoughHealth = target.HP <= (int)(c.CaptureThreshold * (long)health.HP / 100);
 
 				cursor = !capturesInfo.Sabotage || lowEnoughHealth || target.Owner.NonCombatant
 					? capturesInfo.EnterCursor : capturesInfo.SabotageCursor;
diff --git a/OpenRA.Mods.Common/Traits/EmitInfantryOnSell.cs b/OpenRA.Mods.Common/Traits/EmitInfantryOnSell.cs
index 65ec04e343..5dd228b84a 100644
--- a/OpenRA.Mods.Common/Traits/EmitInfantryOnSell.cs
+++ b/OpenRA.Mods.Common/Traits/EmitInfantryOnSell.cs
@@ -60,8 +60,9 @@ namespace OpenRA.Mods.Common.Traits
 			var dudesValue = info.ValuePercent * cost / 100;
 			if (health != null)
 			{
-				if (100 * health.HP >= info.MinHpPercent * health.MaxHP)
-					dudesValue = health.HP * dudesValue / health.MaxHP;
+				// Cast to long to avoid overflow when multiplying by the health
+				if (100L * health.HP >= info.MinHpPercent * (long)health.MaxHP)
+					dudesValue = (int)((long)health.HP * dudesValue / health.MaxHP);
 				else
 					dudesValue = 0;
 			}
diff --git a/OpenRA.Mods.Common/Traits/Explodes.cs b/OpenRA.Mods.Common/Traits/Explodes.cs
index 13647337c2..33167818f1 100644
--- a/OpenRA.Mods.Common/Traits/Explodes.cs
+++ b/OpenRA.Mods.Common/Traits/Explodes.cs
@@ -134,7 +134,8 @@ namespace OpenRA.Mods.Common.Traits
 			if (Info.DamageThreshold == 0)
 				return;
 
-			if (health.HP * 100 < Info.DamageThreshold * health.MaxHP)
+			// Cast to long to avoid overflow when multiplying by the health
+			if (health.HP * 100L < Info.DamageThreshold * (long)health.MaxHP)
 				self.World.AddFrameEndTask(w => self.Kill(e.Attacker));
 		}
 	}
diff --git a/OpenRA.Mods.Common/Traits/Power/ScalePowerWithHealth.cs b/OpenRA.Mods.Common/Traits/Power/ScalePowerWithHealth.cs
index 768f55453d..be8ec4e78e 100644
--- a/OpenRA.Mods.Common/Traits/Power/ScalePowerWithHealth.cs
+++ b/OpenRA.Mods.Common/Traits/Power/ScalePowerWithHealth.cs
@@ -32,7 +32,8 @@ namespace OpenRA.Mods.Common.Traits
 
 		int IPowerModifier.GetPowerModifier()
 		{
-			return 100 * health.HP / health.MaxHP;
+			// Cast to long to avoid overflow when multiplying by the health
+			return (int)(100L * health.HP / health.MaxHP);
 		}
 
 		void INotifyDamage.Damaged(Actor self, AttackInfo e) { power.UpdateActor(self); }
diff --git a/OpenRA.Mods.Common/Traits/SelfHealing.cs b/OpenRA.Mods.Common/Traits/SelfHealing.cs
index 3d85ef2473..19bb2905ed 100644
--- a/OpenRA.Mods.Common/Traits/SelfHealing.cs
+++ b/OpenRA.Mods.Common/Traits/SelfHealing.cs
@@ -55,7 +55,8 @@ namespace OpenRA.Mods.Common.Traits
 			if (self.IsDead || IsTraitDisabled)
 				return;
 
-			if (health.HP >= Info.HealIfBelow * health.MaxHP / 100)
+			// Cast to long to avoid overflow when multiplying by the health
+			if (health.HP >= Info.HealIfBelow * (long)health.MaxHP / 100)
 				return;
 
 			if (damageTicks > 0)
@@ -67,7 +68,9 @@ namespace OpenRA.Mods.Common.Traits
 			if (--ticks <= 0)
 			{
 				ticks = Info.Delay;
-				self.InflictDamage(self, new Damage(-(Info.Step + Info.PercentageStep * health.MaxHP / 100), Info.DamageTypes));
+
+				// Cast to long to avoid overflow when multiplying by the health
+				self.InflictDamage(self, new Damage((int)(-(Info.Step + Info.PercentageStep * (long)health.MaxHP / 100)), Info.DamageTypes));
 			}
 		}
 
diff --git a/OpenRA.Mods.Common/Traits/Sellable.cs b/OpenRA.Mods.Common/Traits/Sellable.cs
index 78a7fd4fc1..dfd1703178 100644
--- a/OpenRA.Mods.Common/Traits/Sellable.cs
+++ b/OpenRA.Mods.Common/Traits/Sellable.cs
@@ -94,14 +94,14 @@ namespace OpenRA.Mods.Common.Traits
 		{
 			get
 			{
-				var sellValue = self.GetSellValue() * info.RefundPercent / 100;
-				if (health.Value != null)
-				{
-					sellValue *= health.Value.HP;
-					sellValue /= health.Value.MaxHP;
-				}
+				var sellValue = self.GetSellValue();
 
-				return "Refund: $" + sellValue;
+				// Cast to long to avoid overflow when multiplying by the health
+				var hp = health != null ? (long)health.Value.HP : 1L;
+				var maxHP = health != null ? (long)health.Value.MaxHP : 1L;
+				var refund = (int)((sellValue * info.RefundPercent * hp) / (100 * maxHP));
+
+				return "Refund: $" + refund;
 			}
 		}
 	}